tipc: Fix recognition of trial period

The trial period exists until jiffies is after addr_trial_end. But as
jiffies will eventually overflow, just using time_after will eventually
give incorrect results. As the node address is set once the trial period
ends, this can be used to know that we are not in the trial period.

Fixes: e415577f

 ("tipc: correct discovery message handling during address trial period")
Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>